Tax On the Gross Amt:- This is the general thing remove the above tick mark and if u click calculate taxes the system will calculate on the gross amount.

Journal Transaction

Tax On the Net Amt

Taxes on the Net amt :- If the tax amounts are to be calculated, you can specify here that the G/L account amounts are to be entered net (i.e. excluding tax). If not, the system assumes that the G/L account amounts entered are gross and not net of tax.